1. Technical Field
The present disclosure relates to a liquid crystal display (“LCD”) device and more particularly to a backlight unit included in an LCD device.
2. Discussion of the Related Art
An LCD device is light weight display device that consumes less power than a display device that is based on a cathode ray tube (“CRT”). The LCD display device may be designed to have a large screen for effective viewing of high-definition video content. Such large screen display devices may have a display that is 30″ or larger. Other recent technologies for producing large screen displays include plasma display panels (“PDP”).
A cold cathode fluorescent lamp (“CCFL”) has conventionally been utilized as a light source for an LCD device. Multiple CCFL circuits are used in a direct type backlight unit for large screen LCD display devices.
In LCD displays, a single AC transformer may not be able to effectively power multiple CCFL circuits owing to the fact that the first-driven CCFL circuit may have a lower impedance than subsequently driven CCFL circuits and this impedance imbalance may make it difficult to balance current between the various CCFL circuits. Accordingly, one or more of the CCFL circuits may not be effectively driven.
Various techniques have been studies to effectively power multiple CCFL circuits using a single AC transformer. For example, a capacitor balancing approach has been developed.
FIG. 1 is a circuit diagram showing a backlight unit using the capacitor balancing method according to the related art. Referring to FIG. 1, a lamp 111 is driven by a transformer 115 via a capacitor 113. The capacitor 113 is electrically connected to the lamp 111 and has an impedance equal to or more than the lamp 111. Even though the plurality of the lamps 111 is driven by a transformer 115, the impedance of the capacitor 113 remains constant, thereby maintaining the current balance.
However, the capacitor used in the capacitor balancing method needs to have a high impedance and thus has difficulty stopping the driving of the lamps in an abnormal driving state.